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It seems Apple's iPad not only has the most available applications and best branding power, but it will also last the longest between plug-ins. A British consumer product-testing watchdog group field-tested a range of popular tablets and found that the hardware brought to life by Apple's late visionary Steve Jobs will outlast Samsung's Galaxy Tab, Sony's Xperia Tablet S, Microsoft's Surface and others, with an impressive 811 minutes -- nearly 14 hours -- of Web browsing over Wi-Fi, or 3G if capable.

The iPad with Retina display fared consider better than its older sibling, the iPad 2, with just 590 minutes.

Both, however, far exceed the average charged time of 451 minutes for 16 tablets 9.7-inches or larger tested by Which?, a non-profit similar to Consumer Reports in the U.S. It does not accept ads for its Web site and magazine and strives to publish expert, unbiased information about products and services.

A separate battery test was conducted for smaller tablets. The results were published on the group's Web site Tuesday.

Leader of the Pack

Second-place bragging rights went to the Xperia, with 534, followed by the Galaxy Tab -- the closest Apple has to a serious tablet competitor and the subject of a patent lawsuit -- with a relatively puny 532 minutes.

The Surface, Microsoft's flagship Windows 8 tablet, will keep you browsing plug-free for 501 minutes, while Google's Nexus Prime, manufactured by Asus, will run for 488 minutes before going dark.

The poorest result was the Asus Eee Pad Transformer Prime (operated without its keyboard), with just 335 minutes of browsing. Add the keyboard, with its additional battery, and you get 661 minutes, Which? said.

The results were similar in the smaller tablet category. Measuring the new kid on the block, the iPad mini, against 7-inch rivals, the Apple cooked the Kindle Fire, with 783 minutes compared with the Amazon tablet's 591, and neutralized the Nexus 7 (550 minutes). The Kindle Fire lasted 437 minutes and the Galaxy Tab 7.0 trailed with just 425 minutes of juice. The average for tablets in the 7-inch range was 478 minutes.

Unlike computer chips, which exponentially increase their storage capacity year after year, manufacturers have not found ways to pack substantially more energy into batteries as more and more features are expected from multi-tasking devices.

Better Power Management

"Battery technologies have not improved significantly in the past several years," said device analyst Jeff Orr of ABI Research.

"The change being observed in mobile device battery life today has more to do with device vendors optimizing how the battery is used -- everything from turning off processor cores when not utilized to low-power mode," Orr told us. "As users engage more frequently with their mobile device, operate over higher-speed mobile broadband networks, and consume more content daily, battery life is increasingly critical to maintaining a good experience."

To keep things fair in the test, Which? kept the screen intensity of each device to 200 nits (a measure of visible light intensity.)